1. Field of the Invention
The present invention relates to rotating electrical machines.
2. Description of the Related Art
Increasingly demanding requirements are continually placed on alternators used in automobiles. The combination of increased electrical power demand and generally smaller vehicles creates the demand for greater electrical power output without a greatly increased size of the alternator. Another demand is for reduced acoustic noise from the alternator. In particular, air flow through the rotor of the alternator can produce bothersome acoustic noise when the rotor rotates.
One way to meet the need for increased power output from an alternator is described in U.S. Pat. No. 4,959,577, issued to Radomski. In this patent, permanent magnets are installed between the pole fingers of an alternator. While this method may provide some advantages in terms of increased power output, other concepts could potentially provide more substantial advantage. Further, other configurations may be more amenable to mass production. Also, other configurations may be able to provide increased power output while additionally reducing the airflow-caused acoustic noise discussed above. Finally, other configurations may be more robust, in terms of surviving high-speed rotation of the alternator rotor and the harsh underhood environment (including vibration) found in automobiles.
As a result, an alternator design which provides increased power output and reduced acoustic noise over conventional designs and which does so in a way that is durable and amenable to mass production will provide advantages over the prior art.